Field of the Invention
This invention relates to emulsion explosives, and more particularly to an emulsion explosive composition that includes voids/bubbles formed from a noble gas dispersed therein.
Description of Related Art
Emulsion explosives have been widely accepted in the explosives industry. These types of explosives are generally understood to include explosive compositions comprised of multiple, immiscible liquids. It is further known that emulsion explosive performance may be enhanced by the addition of a gaseous phase of voids/bubbles, preferably spherical in shape, to facilitate detonation. A reason for this is that during the primary phase of detonation, a super-sonic shock wave travels through the explosive charge which compresses the voids/bubbles contained therein. When the void/bubble rapidly compresses to high pressures, a large amount of heat is generated. Heat created by compressing and collapsing a void/bubble can generate sufficient temperatures to cause the decomposition and subsequent detonation of the surrounding explosive. Voids/bubbles used in emulsion explosives are commonly comprised of nitrogen, oxygen, or a mixture of both (including air). Voids/bubbles are generally added to emulsions by various methods such as, but not limited to, caviation, the addition of pre-manufactured closed celled micro-spheres, or chemical gassing. In recent years, chemical gassing has become the preferred method because of its low cost, excellent dispersion, ease of storage and transport, and density flexibility, among other advantages.
For example, U.S. Pat. No. 4,110,134 to Wade, which is expressly incorporated herein by reference, discusses a water-in-oil emulsion explosive composition that includes an occluded gas as well as an improved sensitizer-catalyst system. U.S. Pat. No. 3,447,978 to Bluhm and U.S. Pat. No. 3,674,578 to Cattermole, both of which are expressly incorporated herein by reference, each describe an emulsion type blasting agent that includes occluded air and offer advantages over slurry type explosives, but are not cap sensitive. U.S. Pat. No. 4,936,933 to Yabsley et al., which is expressly incorporated herein by reference, describes a process for mechanically entraining gas bubbles into an emulsion explosive. More recently, U.S. Pat. No. 8,114,231 to da Silva et al., which is expressly incorporated herein by reference, discusses a method for gassing an emulsion explosive with nitric oxide in order to sensitize the explosive to detonation and/or for density modification.
Despite the focus and advantages of including voids/bubbles within an emulsion explosive composition, very little attention has been given to selecting the type of gas that forms the void.